He served as founding director of the CAS Institute of Physics and the second president of the University of Science and Technology of China (1980–1984).

His Ph.D. dissertation was on the "deformation and change of optical properties of quartz in an electrical field", with Charles Fabry as his advisor.

[5] After returning to China, Yan became Dean of the School of Sciences and Engineering at Jinan University (then located in Shanghai).

On Yan's recommendation, Qian Sanqiang later studied with Joliot-Curie and became one of China's foremost nuclear physicists.

[6] Yan returned to China again in 1930, and soon afterwards became the founding director of the Institute of Physics of the National Peiping Academy in Beiping (now Beijing).

[7] When the Second Sino-Japanese War broke out in 1937 and Beiping came under Japanese attack, Yan organized the arduous relocation of the Institute of Physics to Kunming in southwest China.

Under his leadership and aided by Qian Linzhao, the institute manufactured hundreds of high-powered microscopes, crystal oscillators, military rangefinders and telescopes, and other equipment.

[4][7] After the founding of the People's Republic of China in 1949, Yan was instrumental in the establishment of the Chinese Academy of Sciences (CAS).

The fourth, Yan Siguang (严四光), was a distinguished researcher at the Chinese Academy of Social Sciences.